Bi-direction constant current device

Abstract

An LED lamp includes a bi-direction constant current device coupled between a power supply and a LED load to provide stable positive and negative currents to the LED load. The bi-direction constant current device includes a pair of current sources face-to-face or back-to-back connected in series between the power supply and the LED load, and two protective elements shunt to the pair of current sources, respectively.

1. A bi-direction constant current device for providing current to a load, comprising:
 two connecting terminals; 
 two current sources connected in series between the two connecting terminals; 
 a first protective element connected in parallel to the first current source; and 
 a second protective element connected in parallel to the second current source; 
 wherein the first current source and the second protective element establish a first current flowing from the first connecting terminal to the second connecting terminal in a first state, the second current source and the first protective element establish a second current flowing from the second connecting terminal to the first connecting terminal in a second state. 
 
     
     
       2. The bi-direction constant current device of  claim 1 , wherein the two current sources are back-to-back connected to each other. 
     
     
       3. The bi-direction constant current device of  claim 1 , wherein the two current sources are face-to-face connected to each other. 
     
     
       4. The bi-direction constant current device of  claim 1 , wherein the first current source is off in the second state. 
     
     
       5. The bi-direction constant current device of  claim 1 , wherein the second current source is off in the first state. 
     
     
       6. The bi-direction constant current device of  claim 1 , wherein the first protective element is open circuit in the first state. 
     
     
       7. The bi-direction constant current device of  claim 1 , wherein the second protective element is open circuit in the second state. 
     
     
       8. The bi-direction constant current device of  claim 1 , wherein the first protective element bypasses the first current source in the second state. 
     
     
       9. The bi-direction constant current device of  claim 1 , wherein the second protective element bypasses the second current source in the first state. 
     
     
       10. The bi-direction constant current device of  claim 1 , wherein the first protective element comprises a diode. 
     
     
       11. The bi-direction constant current device of  claim 1 , wherein the second protective element comprises a diode. 
     
     
       12. The bi-direction constant current device of  claim 1 , wherein the first and second currents are equal in magnitude. 
     
     
       13. The bi-direction constant current device of  claim 1 , wherein the first and second currents are different in magnitude. 
     
     
       14. The bi-direction constant current device of  claim 1 , wherein the first current source comprises:
 a positive voltage terminal and a negative voltage terminal; 
 two transistors connected in series between the positive and negative voltage terminals; 
 a resistor coupled between the positive voltage terminal and a control electrode of the first transistor; 
 a Zener diode coupled between the control electrode of the first transistor and the negative voltage terminal; and 
 a control circuit coupled to a control electrode of the second transistor. 
 
     
     
       15. The bi-direction constant current device of  claim 1 , wherein the second current source comprises:
 a positive voltage terminal and a negative voltage terminal; 
 two transistors connected in series between the positive and negative voltage terminals; 
 a resistor coupled between the positive voltage terminal and a control electrode of the first transistor; 
 a Zener diode coupled between the control electrode of the first transistor and the negative voltage terminal; and 
 a control circuit coupled to a control electrode of the second transistor. 
 
     
     
       16. An LED lamp, comprising:
 two power input terminals for being coupled to a power supply; 
 a LED load; and 
 a bi-direction constant current device connected in series with the LED load between the two power input terminals, providing a first current in a first direction to the LED load in a first state, and a second current in a second direction to the LED load in a second state. 
 
     
     
       17. The LED lamp of  claim 16 , wherein the bi-direction constant current device comprises:
 two current sources connected in series; 
 a first protective element connected in parallel to the first current source; and 
 a second protective element connected in parallel to the second current source; 
 wherein the first current source and the second protective element establish the first current in the first state, and the second current source and the first protective element establish the second current in the second state. 
 
     
     
       18. The LED lamp of  claim 17 , wherein the two current sources are back-to-back connected to each other. 
     
     
       19. The LED lamp of  claim 17 , wherein the two current sources are face-to-face connected to each other. 
     
     
       20. The LED lamp of  claim 17 , wherein the first current source is off in the second state. 
     
     
       21. The LED lamp of  claim 17 , wherein the second current source is off in the first state. 
     
     
       22. The LED lamp of  claim 17 , wherein the first protective element is open circuit in the first state. 
     
     
       23. The LED lamp of  claim 17 , wherein the second protective element is open circuit in the second state. 
     
     
       24. The LED lamp of  claim 17 , wherein the first protective element bypasses the first current source in the second state. 
     
     
       25. The LED lamp of  claim 17 , wherein the second protective element bypasses the second current source in the first state. 
     
     
       26. The LED lamp of  claim 17 , wherein the first protective element comprises a diode. 
     
     
       27. The LED lamp of  claim 17 , wherein the second protective element comprises a diode. 
     
     
       28. The LED lamp of  claim 17 , wherein the first and second currents are equal in magnitude. 
     
     
       29. The LED lamp of  claim 17 , wherein the first and second currents are different in magnitude. 
     
     
       30. The LED lamp of  claim 17 , wherein the first current source comprises:
 a positive voltage terminal and a negative voltage terminal; 
 two transistors connected in series between the positive and negative voltage terminals; 
 a resistor coupled between the positive voltage terminal and a control electrode of the first transistor; 
 a Zener diode coupled between the control electrode of the first transistor and the negative voltage terminal; and 
 a control circuit coupled to a control electrode of the second transistor. 
 
     
     
       31. The LED lamp of  claim 17 , wherein the second current source comprises:
 a positive voltage terminal and a negative voltage terminal; 
 two transistors connected in series between the positive and negative voltage terminals; 
 a resistor coupled between the positive voltage terminal and a control electrode of the first transistor; 
 a Zener diode coupled between the control electrode of the first transistor and the negative voltage terminal; and 
 a control circuit coupled to a control electrode of the second transistor. 
 
     
     
       32. The LED lamp of  claim 16 , wherein the LED load comprises:
 two connecting terminals; and 
 a plurality of LED pairs connected in series between the two connecting terminals, each LED pair having two parallel connected LEDs oriented in two directions. 
 
     
     
       33. The LED lamp of  claim 16 , wherein the LED load comprises:
 two connecting terminals; 
 a first LED string oriented in the first direction, connected between the two connecting terminals; and 
 a second LED string oriented in the second direction, connected between the two connecting terminals. 
 
     
     
       34. The LED lamp of  claim 16 , wherein the LED load comprises:
 two connecting terminals; and 
 a LED bridge connected between the two connecting terminals, having a plurality of first LEDs oriented in the first direction and a plurality of second LEDs oriented in the second direction. 
 
     
     
       35. The LED lamp of  claim 16 , wherein the LED load comprises an alternating current LED chip. 
     
     
       36. The LED lamp of  claim 16 , further comprising a lamp base having two electrodes coupled to the two power input terminals, respectively. 
     
     
       37. The LED lamp of  claim 36 , further comprising a lamp shell secured in position to the lamp base.